90psi after KZ1100 head on KZ1000

I have a running 1980KZ1000 ltd that is blowing a little bit of smoke and making strange nosies from the top end. It has 59000 miles, compression not bad 110psi in 2 holes and 120psi in the other two. I know its below stock but made decent power. The only reason I took it apart was the weird sounds of the topend. Turns out the cam chain assembly was really worn badly. Got a low milage system from a junk yard. the exhaust guides were worn the intakes too. Needed rebuilt head. I actually bought a rebuilt head from a guy before I took apart the motor to limit down time. But It was for a 1100 KZ1100ST. At the time I did not think at all about the difference in engine size, bore?. So I installed it on the KZ1000 lower end along with low milage pistons and rings for a 1000cc std bore. Set the valves timing is dead on and only came up with 90 psi dead even across all four barrels. Did I loose the psi because of the 1100 head?. Or do I need to rebuild the original 1000 head to match up?

Post edited by: ltd1000, at: 2007/07/02 23:10

the bad news is if that is a j series head you put on there your compression went from around 8.3:1 to 6.3:1 about the same as a model A because of the bigger combustion chamber.the good news is it should run on anykind of cheap gas you can get;)

boost it!!

RollingStock wrote:

boost it!!

AGREED!

did you use the stock 1000 block/pistons or do you swap in the 1100 block and pistons?

Post edited by: themachine, at: 2007/07/02 18:58

Interesting, How do you tell a J spec head to a non j head pre 81 with it mounted on the engine? I believe the J head came out in 1981 with the redesigned overall bike?. If the head turns out to be pre 1981 will the larger 1100 combustion chamber still lower the psi so dramaticaly in the cylinders? So this raises the question of cc capacity of 1000 vs 1100. Where do I find that spec? Thanks, Mike.. If this proves to be my problem can I make up the psi with a thinner head gasket? Or will I have to Reinstall the orignal 1000 head? That will mean a rebuild of it.

a J head and pre 80 block will not interchange ( i belive)

are you using the jugs and pistons from the 1100?

i thought the 1100 had smaller or bigger pins, are they the same stroke too?

on a J head the cam covers arnt rounded on the ends, they are square and boxy and obviously different from the early heads.

if you use the head, block and pistons from the 1100 it should turn out good, did you turn the engine over four times with the throttle wide open when you tested it? did you try squirting oil in there?

So you installed a 1981 KZ1100 Shaft cylinder head on a 1980 KZ1000?

The 81 KZ1100 motor used a HyVo cam chain, while the 80 KZ1000 motor used a roller cam chain, so did you get the adapter from APE to enable you to use the roller cam chain with the 81 1100 head? If not, then I'm kind of doubtful that you have a 1100 head.

Have you read www.aperaceparts.com/tech/techkz1000.html

To use the head, block and pistons off a 81 or newer 1000 (except the 81 cop bike) or 1100, it won't work, the rods on the later motors are different (read the link above).

Post edited by: steell, at: 2007/07/03 00:12

Are you sure you don't have an early 81 LTD titled
as an 80? That is the only way a head off an 1100
would bolt right on.

Ok, Think I have it fiqured out. No jspec head used on my 1015L cylinders,pistons (std bore). Simply a cause of 1100L head (pre 1981) mounted on a 1015L mtr. The larger combustion chamber causing the drop in psi. So the cure well be to put back on the original 1015L head which should bring back the lost psi. Thanks for the ideas...

Tjettim is our winner.No way an 1100 head will bolt on a 1000 as lots have pointed out.Titles in USA seem to be inaccurate more than we see in Canada, see 76's titled as 75's etc. the time on ebay.